1. Field of the Invention
The present invention relates to a cutting method for cutting the end face of a sheet member, a manufacturing method of a sheet member having a cutting step with the method, a sheet member with the end face cut with the cutting method, and an optical element and an image display device equipped with the sheet member, and is effective on a sheet member which requires especially high precision end face machining.
2. Description of the Related Art
An example of a sheet member that requires especially high precision end face machining is a film for optical use such as a polarizing plate. The polarizing plate is used in many situations as a constituting member of a liquid crystal display device (may be referred to as LCD below), and in recent years, its demand has been increasing rapidly. Moreover, use of a polarizing plate of high added value with optically compensating functions, brightness improving functions, etc. is increasing, and the demand for display quality tends to increase more. A polarizing plate is generally used in which a protective film such as triacetyl cellulose (may be referred to as TAC below) is laminated on the both faces of a polarizing film consisting of a polyvinyl alcohol based film on which adsorption and orientation of iodine or a dichroic dye is performed. Further, a polarizing plate is also used depending on the objectives when a film having optical compensating functions and brightness improving functions is laminated through an agglutinant or an adhesive.
In order to mount a polarizing plate on a LCD panel, the polarizing plate is required to be machined into a predetermined shape and dimension, and it is very important to finish the end face with high precision and in good condition for the polarizing plate to be mounted on a narrow framed panel. Generally, a raw sheet of a lengthy form of a mono-layered sheet or a multi-layered sheet (for example, one that is formed with an optical film layer and an adhesive layer and is called a laminated film) is cut into a rectangular shape using a blanking blade die, etc. This sheet member is expanded in the uniaxial or biaxial direction, and the cutting is performed without concern for the direction of the extension. However, there is a problem that fiber-shaped broken pieces attaching to the end face of the cut sheet member (a cut surface) and adhesive squeezing-out from the end face by the pressure of the cutting cause deterioration in the appearance and deterioration in quality.
In the cutting method disclosed in Japanese Patent Application Laid-Open No. 2004-148419 described below, a copying roller 14 shown in FIG. 9 is used. This copying roller 14 is always pressed onto a copying mold 13, and by cutting the end face of a sheet member 11 with a rotating blade 12 installed on the core of the roller, fiber-shaped broken pieces attached on the end face can be removed. However, in this method, because the rotating blade 12 projecting in the radial direction contacts with the end face of the sheet member 11 at equal intervals while being pressed as shown in FIG. 10, striped cutting traces are deeply formed on the end face and there is a problem that the appearance deteriorates and a sufficient dimensional accuracy cannot be obtained.